Looks like optical flow with the direction of the flow has been mapped to hue.

Edit: as in compute the optical flow for every pair of consecutive frames. Probably would need to stabile the source video first. That might be why the colors of the four corners stays mostly the same, since if you were moving forwards you would expect the overall flow to be from the centre of the frame outwards.

Digitally painted individual elements, which are then animated, I think. Don’t quote me on that tho.

Edit: Could actually be done in Blender, because of the depth. Just a guess.